Highly Effective Biocides against Pseudomonas\naeruginosa Reveal New Mechanistic Insights Across\nGram-Negative Bacteria

Pseudomonas\naeruginosa is a major\nnosocomial pathogen that persists in healthcare settings despite rigorous\ndisinfection protocols due to intrinsic mechanisms conferring resistance.\nWe sought to systematically assess cationic biocide efficacy against\nthis pathogen using a panel of multidrug-resistant P. aeruginosa clinical isolates. Our studies revealed\nwidespread resistance to commercial cationic disinfectants that are\nthe current standard of care, raising concerns about their efficacy.\nTo address this shortcoming, we highlight a new class of quaternary\nphosphonium compounds that are highly effective against all members\nof the panel. To understand the difference in efficacy, mechanism\nof action studies were carried out, which identified a discrete inner-membrane\nselective target. Resistance selection studies implicated the SmvRA\nefflux system (a transcriptionally regulated, inner membrane-associated\nefflux system) as a major determinant of resistance. This system is\nalso implicated in resistance to two commercial bolaamphiphile antiseptics,\noctenidine and chlorhexidine, which was further validated herein.\nIn sum, this work highlights, for the first time, a discrete inner-membrane\nspecific mechanism for the bolaamphiphile class of disinfectants that\ncontrasts with the prevailing model of indiscriminate membrane interactions\nof commercial amphiphiles paving the way for future innovations in\ndisinfectant research.